Pigmented coating compositions are useful for their aesthetic as well as protective features. The coating compositions contain a film-forming resin and a pigment dispersed in a liquid carrier. It is important that the pigment be satisfactorily dispersed throughout any film which results from the application of the coating composition. Accordingly it is imperative that the pigment be well dispersed throughout the liquid coating composition. Normally the pigment to be used is first dispersed in a liquid with a dispersant, sometimes referred to as a grinding aid. The resulting dispersion is then mixed with the main film-forming resin of the composition and any other necessary components to produce the final coating composition.
A large number of different dispersants have been used in the manufacture of pigmented coating compositions. The dispersants have typically been low molecular weight surfactants and in a limited sense polymeric materials, all of which are capable of dispersing the pigment in a liquid carrier. A problem which has been widely experienced with the low molecular weight materials is their tendency to exude from the painted film after prolonged weathering. This can result in an undesirable appearance. Another problem which has been experienced with the conventional dispersants has been their tendency to cause the paint film to be tacky. Sometimes prolonged aging will remove this problem; however the problem manifests itself mainly with freshly painted film around windows and doors which must be closed a short time after being painted. The tackiness of the paint film can result in the window or door being stuck to its frame.
There now have been found dispersants based on polymerization products which contain a high oxyalkylene content. Such dispersants are useful for dispersing pigments which can then be used in resin containing coating compositions without contributing to film tack.
As used herein all percentages and ratios are by weight unless otherwise indicated.